| 1. |
- Blute, I, et al.
(author)
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Phase behaviour of alkyl glycerol ether surfactants
- 1998
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In: Tenside Surfactants Detergents. - 0932-3414 .- 2195-8564. ; 35, s. 207-212
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Journal article (peer-reviewed)abstract
- In this paper the phase behaviour and physical properties of a series of alkyl (C6, C8, C12 and iso-C8) monoglycerol ethers and 2-hydroxyalkyl (C6, C8, C12) monoglycerol ethers are presented. The binary phase diagram for the surfactants shows very little dependence on temperature. It is shown that as the alkyl chain length increases the tendency to form lamellar liquid crystalline phases increases. The branched alkyl chain shows no formation of lamellar phase even at high concentrations of surfactant. The differences in phase behaviour between the surfactants is attributed to the variation in the critical packing parameter (CPP) of the surfactants. The presence of an additional hydroxyl group in the alkyl chain causes a temperature independent solubility behaviour. Ternary phase diagrams were prepared using dodecane as the oil phase. Hexyl glycerol ether was the only of the alkyl glycerol ethers which was sufficiently water soluble to determine the surface tension and CMC. The CMC was determined to 15 mM (and surface tension to 26 mN m-1).
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| 2. |
- Costas, M, et al.
(author)
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Thermodynamics of aliphatic and aromatic hydrocarbons in water
- 1998
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In: Biophysical Chemistry. - 0301-4622 .- 1873-4200. ; 74, s. 83-87
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Journal article (peer-reviewed)abstract
- Makhatadze and Privalov have analyzed the thermodynamics of transfer of aliphatic and aromatic hydrocarbons from the gas phase into water. Finding that the hydration free energy of aliphatic and aromatic hydrocarbons trave different signs, they conclude that the mechanism causing hydrophobicity of these solutes is of a different nature. Here, we offer an alternative analysis of the dissolution of these non-polar compounds into water based on a recently published interpretation scheme for thermodynamic transfer functions. Our analysis shows that the hydrophobicity of aromatic and aliphatic hydrocarbons is qualitatively the same, i.e. its causes are the same namely the extremely high cohesive energy of water which overcomes the favorable solute-solute and solute-water interactions. However, both analyses conclude that the experimentally observed quantitative difference between the interactions of water with aliphatic and aromatic hydrocarbons, can be assigned to the formation of aromatic ring-water H-bonds.
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| 3. |
- Jha, BK, et al.
(author)
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Titration microcalorimetry studies of the interaction between humicola lanuginosa lipase and ionic surfactants
- 1999
-
In: Journal of Colloid and Interface Science. - 0021-9797 .- 1095-7103. ; 213, s. 262-264
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Journal article (peer-reviewed)abstract
- Microcalorimetry has been used to study the interaction between Humicola lanuginosa lipase and either the anionic surfactant sodium dodecyl sulfate, SDS, or the cationic surfactant tetradecyltrimethylammonium bromide, TTAB. For SDS no conclusive evidence was obtained of whether or not an enzyme-surfactant complex is formed. Although not unambiguous, the calorimetric titration curves obtained with TTAB indicate formation of such a complex.
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| 4. |
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| 5. |
- Kronberg, B, et al.
(author)
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On understanding hydrophobicity : Chapter 7
- 1996
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In: New Horizons. - : AOCS Press. ; , s. 63-69
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Book chapter (peer-reviewed)abstract
- In phenomena such as micellization, solubilization and detergency the hydrophobicity is the driving force. This force causes nonpolar parts of surfactant molecules to minimize their contact with water. It is shown that the adsorption of surfactants on hydrophobic surfaces, such as latexes, is totally dominated by the hydrophobic effect. Thus, the nature of the latex particle surface only plays a minor role. The adsorption of surfactants on hydrophobic surfaces is therefore akin to micellization. Thermodynamic analysis of these phenomena reveal that the hydrophobic effect consists of two parts. The first part is due to the structuring of water molecules around a hydrophobic group resulting in a decrease in entropy, enthalpy as well as Gibbs free energy. It is thus favourable and counteracts the hydrophobic effect. The second contribution is due to the large amount of energy that is required to form a cavity in the water in order to accommodate a hydrophobe This contribution is attributed to the large cohesive energy density in water, which in turn is due to the small size of water molecules, meaning that many hydrogen bonds have to be broken in order to form a cavity for the hydrophobe. This second contribution dominates over the first one and is the cause for the hydrophobic effect. On the other hand the temperature dependence of the hydrophobic effect is totally dominated by the first contribution i.e. the water structuring.
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| 6. |
- Kronberg, B
(author)
-
Surfactant mixtures
- 1997
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In: Current Opinion in Colloid & Interface Science. - 1359-0294 .- 1879-0399. ; 2, s. 456-463
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Journal article (peer-reviewed)abstract
- The interest in mixed surfactant systems is continuously increasing. The development during the last years has mainly been focused on (i) the theoretical description of mixed micelles, (ii) the coexistence of two types of micelles, one rich in one of the surfactants and the other rich in the other surfactant, and (iii) mixtures of cationic and anionic (catanionics) surfactants forming systems in which vesicles and other intricate structures appear. This review also touches on surfactant mixtures at surfaces as well as on some examples of technical applications.
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| 7. |
- Kronberg, B, et al.
(author)
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Thermodynamics of the hydrophobic effect in surfactant solutions – micellization and adsorption
- 1995
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In: Pure and Applied Chemistry. - 0033-4545 .- 1365-3075. ; 67, s. 897-902
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Journal article (peer-reviewed)abstract
- The thermodynamics of surfactant micellization and adsorption onto hydrophobic surfaces are examined. The ideal and the Flory-Huggins approximations for the combinatorial entropy of transfer are contrasted. Two main contributions for the Gibbs free energy of transfer from the aqueous solution to the micelle or the surface are considered. The first is the collapse of the water cavity left behind when the solute is transferred and the second is the destruction of the water structuring around the solute. It is the balance between these two contributions which causes the minimum in critical micelle concentration and the maximum in adsorption of ionic surfactants with temperature. Separation of these two contributions is achieved using a two-state model recently reported for water molecules around non-polar solutes.
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| 8. |
- Mancera, RL, et al.
(author)
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Thermodynamics of the hydration of non-polar substances
- 1998
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In: Biophysical Chemistry. - 0301-4622 .- 1873-4200. ; 70, s. 57-63
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Journal article (peer-reviewed)abstract
- We re-examine the numerical value and physical significance of TS , the temperature where the entropy of transfer Δ WLCP fitting function. It is concluded that the interpretation of TS as the temperature where hydration ceases cannot be sustained. As previously reported [R.L. Baldwin, N. Muller, Proc. Natl. Acad. Sci. USA, 89 (1992) 7110], hydration must vanish at a temperature T1 >TS, where its experimental manifestation, i.e., ΔWL CP, is zero. We discuss the concept of water relaxation around a non-polar solute molecule and its relation to the hydration process.
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| 9. |
- Monnereau, C, et al.
(author)
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Influence of gravity on foams
- 1999
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In: J Chim Phys-Chim Biol. - 0021-7689. ; 96, s. 958-967
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Journal article (peer-reviewed)abstract
- The feasibility of experiments on the physics of foams in microgravity environment was investigated during a parabolic flight campaign. Transient foams from surfactant-free organic liquids and stable foams from a soapy solution of a Sodium Dodecyl Sulfate + Dodecanol mixture were investigated. In 0g, the transient foam is stabilized; whatever the liquid the foam bubbles are spherical and their diameter does not change during the flight. When the gravity constant is equal to 1.8 g, the bubbles of the stable foam become polyhedral and numerous topological transformations could be observed.
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| 10. |
- Svanholm, T, et al.
(author)
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Adsorption studies of associative interactions between thickener and pigment particles
- 1997
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In: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 30, s. 167-171
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Journal article (peer-reviewed)abstract
- Adsorption of a HEUR thickener and a HMHEC thickener have been studied on two titanium dioxide pigment grades with and without dispersant previously adsorbed. One of the pigments had an acidic surface, mainly silica, and the other a more basic alumina/zirconia surface. Both associative thickeners adsorbed on pigments having a partially hydrophobic (alpha-olefinic maleic acid co-polymer) dispersant preadsorbed on the surface. No adsorption takes place when sodiumhexametaphosphate, a highly charged low molecular weight inorganic dispersant, was used. The alpha-olefinic-maleic acid co-polymer dispersant is shown to adsorb on a negatively charged silica surface. This is assigned to hydrogen bonding between unionised carboxylic groups from the dispersant and oxide ions on the pigment surface.
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